/Engine/Source/Editor/UnrealEd/Classes/ThumbnailRendering/ThumbnailManager.h
Event that is being broadcasted when a thumbnail gets dirtied. Parameter is the object soft object path associated with the thumbnail.
[FOnThumbnailDirtied](API\Editor\UnrealEd\ThumbnailRendering\FOnThumbnailDirtied) & GetOnThumbnailDirtied()